Our objective is to increase our understanding of cellular mechanisms involved in implantation of the blastocyst. Of primary importance will be a series of studies of the normal differentiation of the blastocyst, adhesion and uterine penetration in primates, using the rhesus monkey and the baboon. The cytology of these stages will be examined using both transmission and scanning electron microscope methods following perfusion fixation. In addition, studies of the surface membrane components of both trophoblast and uterine luminal epithelium at the site of implantation will be continued. Scanning electron microscopy of perfused and opened uteri will be used to determine the way in which the blastocyst becomes oriented following induction of implantation during delayed implantation. Studies of the cell biology of uterine gland secretion using radioautography followed by both light and electron microscopy will be completed.